An expression used to describe a sheep (ewe) that has been trained to remain still when her hind legs are placed in a pair of boots for the purpose of facilitating human-to-sheep sexual contact. "Boot broke" is often used to describe a person who is easily controlled or intimidated so that he or she falls in line with another's wishes.
A variant of boot broke is "stump broke," which refers to a cow that has been trained to remain still while someone stands behind her on a stump. Heard in Wyoming, USA.

"Wow, you'd think that Congress would have a problem with Bush and his whole 'unitary executive' thing, but he seems to have the whole place boot broke."